/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.io;

import java.io.*;
import java.net.Socket;

import org.apache.commons.logging.Log;

import org.apache.hadoop.conf.Configuration;

/**
 * An utility class for I/O related functionality.
 */
public class IOUtils {

	/**
	 * Copies from one stream to another.
	 * 
	 * @param in
	 *            InputStrem to read from
	 * @param out
	 *            OutputStream to write to
	 * @param buffSize
	 *            the size of the buffer
	 * @param close
	 *            whether or not close the InputStream and OutputStream at the
	 *            end. The streams are closed in the finally clause.
	 */
	public static void copyBytes(InputStream in, OutputStream out,
			int buffSize, boolean close) throws IOException {

		PrintStream ps = out instanceof PrintStream ? (PrintStream) out : null;
		byte buf[] = new byte[buffSize];
		try {
			int bytesRead = in.read(buf);
			while (bytesRead >= 0) {
				out.write(buf, 0, bytesRead);
				if ((ps != null) && ps.checkError()) {
					throw new IOException("Unable to write to output stream.");
				}
				bytesRead = in.read(buf);
			}
		} finally {
			if (close) {
				out.close();
				in.close();
			}
		}
	}

	/**
	 * Copies from one stream to another. <strong>closes the input and output
	 * streams at the end</strong>.
	 * 
	 * @param in
	 *            InputStrem to read from
	 * @param out
	 *            OutputStream to write to
	 * @param conf
	 *            the Configuration object
	 */
	public static void copyBytes(InputStream in, OutputStream out,
			Configuration conf) throws IOException {
		copyBytes(in, out, conf.getInt("io.file.buffer.size", 4096), true);
	}

	/**
	 * Copies from one stream to another.
	 * 
	 * @param in
	 *            InputStrem to read from
	 * @param out
	 *            OutputStream to write to
	 * @param conf
	 *            the Configuration object
	 * @param close
	 *            whether or not close the InputStream and OutputStream at the
	 *            end. The streams are closed in the finally clause.
	 */
	public static void copyBytes(InputStream in, OutputStream out,
			Configuration conf, boolean close) throws IOException {
		copyBytes(in, out, conf.getInt("io.file.buffer.size", 4096), close);
	}

	/**
	 * Reads len bytes in a loop.
	 * 
	 * @param in
	 *            The InputStream to read from
	 * @param buf
	 *            The buffer to fill
	 * @param off
	 *            offset from the buffer
	 * @param len
	 *            the length of bytes to read
	 * @throws IOException
	 *             if it could not read requested number of bytes for any reason
	 *             (including EOF)
	 */
	public static void readFully(InputStream in, byte buf[], int off, int len)
			throws IOException {
		int toRead = len;
		while (toRead > 0) {
			int ret = in.read(buf, off, toRead);
			if (ret < 0) {
				throw new IOException("Premeture EOF from inputStream");
			}
			toRead -= ret;
			off += ret;
		}
	}

	/**
	 * Similar to readFully(). Skips bytes in a loop.
	 * 
	 * @param in
	 *            The InputStream to skip bytes from
	 * @param len
	 *            number of bytes to skip.
	 * @throws IOException
	 *             if it could not skip requested number of bytes for any reason
	 *             (including EOF)
	 */
	public static void skipFully(InputStream in, long len) throws IOException {
		while (len > 0) {
			long ret = in.skip(len);
			if (ret < 0) {
				throw new IOException("Premeture EOF from inputStream");
			}
			len -= ret;
		}
	}

	/**
	 * Close the Closeable objects and <b>ignore</b> any {@link IOException} or
	 * null pointers. Must only be used for cleanup in exception handlers.
	 * 
	 * @param log
	 *            the log to record problems to at debug level. Can be null.
	 * @param closeables
	 *            the objects to close
	 */
	public static void cleanup(Log log, java.io.Closeable... closeables) {
		for (java.io.Closeable c : closeables) {
			if (c != null) {
				try {
					c.close();
				} catch (IOException e) {
					if (log != null && log.isDebugEnabled()) {
						log.debug("Exception in closing " + c, e);
					}
				}
			}
		}
	}

	/**
	 * Closes the stream ignoring {@link IOException}. Must only be called in
	 * cleaning up from exception handlers.
	 * 
	 * @param stream
	 *            the Stream to close
	 */
	public static void closeStream(java.io.Closeable stream) {
		cleanup(null, stream);
	}

	/**
	 * Closes the socket ignoring {@link IOException}
	 * 
	 * @param sock
	 *            the Socket to close
	 */
	public static void closeSocket(Socket sock) {
		// avoids try { close() } dance
		if (sock != null) {
			try {
				sock.close();
			} catch (IOException ignored) {
			}
		}
	}

	/**
	 * /dev/null of OutputStreams.
	 */
	public static class NullOutputStream extends OutputStream {
		public void write(byte[] b, int off, int len) throws IOException {
		}

		public void write(int b) throws IOException {
		}
	}
}
